1. Field of the Invention
The present invention relates to connector clips of the type used to connect a plurality of signal transmission lines, such as shock tube, in signal transfer proximity to the explosive end of a detonator. More particularly, the present invention concerns a connector clip which enables fast and easy loading of one or a plurality of signal transmission lines through an access opening into a slot, followed by closing the access opening by means of a closure member.
2. Related Art
Connector clips for connecting one or a plurality of outgoing signal transmission lines, such as shock tubes, in signal transfer communication with a detonator mounted in the clip are well-known in the art.
U.S. Pat. No. 5,171,935, issued Dec. 15, 1992 to Richard J. Michna et al. for “Low-Energy Blasting Initiation System Method and Surface Connection Thereof”, and its grandchild continuation case, U.S. Pat. No. 5,398,611 of Richard J. Michna et al. entitled “Low-Energy Blasting Initiation System, Method and Surface Connection Therefor”, each shows a connector clip in which up to four outgoing signal transmission lines, in this case, shock tubes, are disposed within a slot in the clip in signal transfer communication with a low-energy detonator disposed in the body of the clip. Such connector clips are conventionally employed on the surface of a shot field and low-energy detonators are usually employed in the clips in order to reduce noise and the throwing of shrapnel which might prematurely sever connecting lines.
A typical blasting arrangement using such connector clips is schematically illustrated in FIG. 5 of the above-mentioned Michna et al. patents. As shown therein, the connector clips are employed on the surface to transmit signals via connector lines to detonators in a series of boreholes containing explosive charges. Such connector lines are subject to significant tensile stresses during assembly of the shot, as lines are often dragged over rough terrain, played out from borehole to borehole and pulled on to reach connection points. There are two conflicting objectives involved in such assembly operations. It is desired to insert the lines, e.g., shock tubes (40) of the Michna et al. patents, into a line-retaining slot, e.g., slot (37) of FIG. 4 of the Michna et al. patents, as quickly and as easily as possible. On the other hand, once inserted, the shock tubes (40) must resist being pulled out of the slot (37) by tensile stresses imposed on the shock tubes during preparation of the shot. These conflicting objectives may be referred to as the (signal transmission) line insertion and retention problem.
The Michna et al. patents address the line insertion and retention problem by providing the structures (e.g., 42, 43 of FIG. 2) to render the access opening to the slot (37) somewhat smaller than the outside diameters of the tubes (40). See, for example, U.S. Pat. No. 5,171,935 at column 4, lines 56-66. While this expedient helps to retain the tubes (40) in place within slot (37), it creates difficulty in inserting plastic shock tubes or other signal transmission lines into the slot in the first place, especially in cold weather. Shock tubes become less malleable in cold weather, creating difficulty in compressing the tubes sufficiently to squeeze them through the small access opening. The problem is compounded by the fact that changes in temperature cause slight, but not insignificant, changes in the tube outside diameter and in the width of the opening itself. The Michna '935 Patent discloses at column 4, lines 36-38, that segment 36 is “a resiliently deformable segment” and at column 4, lines 48-50, it is stated that the segment 36 is of reduced thickness relative to the housing “thereby allowing it to flex or bend under force.” It appears that this flexibility is designed to accommodate the fact that, as disclosed at column 4, lines 56-59, the width of the line-receiving slot 37 “is slightly smaller than the outside diameter of a transmission tube 40 to securely hold each tube . . . ” It appears that the flexibility of neck 36 enables the retaining member 35 to flex somewhat to accommodate the oversized (relative to the width of the line-retaining slot) transmission tubes 40.
Generally, up to six or so shock tubes or other signal transmission lines may have to be inserted into the line-retaining slot. For example, U.S. Pat. No. 5,792,975 of Thomas C. Tseka et al. for “Connector Block Having Detonator-Positioning Locking Means”, shows a generally C-shaped arcuate slot 15 (FIG. 2) within which six shock tubes (40) are retained. It will be noted from FIG. 2A of the Tseka et al. patent that the opening (38) through which the shock tubes are laterally inserted into the C-shaped slot is shown significantly smaller than the outside diameter of the shock tubes retained therein. Like the Michna et al. patents described above, this configuration suffers from the same difficulties in inserting the shock tubes (40) into the C-shaped slot.
U.S. Pat. No. 5,204,492, issued Apr. 20, 1993 to Merritt Jacob et al. for “Low Noise, Low Shrapnel Detonator Assembly For Initiating Signal Transmission Lines”, addresses the tube insertion and retention problem by providing a closure means which is movable between an open and a closed position so that the shock tubes (14b in FIGS. 4-6 and 8) may be inserted adjacent the explosive end of a detonator retained in the connector clip (in this case, the tubes lie parallel to the longitudinal axis of the detonator to gain the purported advantages described in the Jacob et al. Patent). After the tubes are inserted while the closure means is in the open position (FIG. 10) the closure means are then closed to lock the tubes in place. See column 6, line 55 through column 7, line 44 of the Jacob et al. Patent.
Connector clips used in the field lie on the ground and are exposed to sand, dirt, small particles of rock and other solid foreign material. Entry of such solid foreign material to the travel path of the closure means (e.g., item (42) in FIG. 10 of the Jacob et al. Patent) will interfere with or even preclude secure locking of the closure means to retain the tubes (14b) in place. Obviously, if the locking is not secure, one or more of the tubes inserted into the line-retaining slot may be pulled free by tensile forces acting on the tubes during preparation of the shot, resulting in mis-fires. The Jacob et al. patent also provides for inserting the shock tubes (14b) transversely of the detonator, which is the common and usually preferred practice. However, in the illustration of this embodiment in FIG. 11, Jacob et al. does not provide closure means movable between an open and closed position. Instead there is a conventional entry slot (34 in FIG. 11 of the Jacob et al. patent) which has an entrance to the C-shaped slot which entrance, as illustrated in FIG. 11, appears to be smaller than the outside diameter of the shock tubes (14b). At column 7, lines 51-53, Jacob et al. does state with respect to FIG. 11 that a “closure can also be attached to the confining wall to close gap 34.” The construction of such closure means is not described or illustrated.